A) Field of the Invention
The present invention relates to optical information recording/playback devices which effect recording and/or playback of information by radiating an optical beam onto the surface of an optical information recording medium such as an optical disk. More particularly the present invention relates to a combined-use optical information recording/playback device in which it is possible to effect recording and/or playback of information on optical information recording media having different specifications using a single device, irrespective of the method of encoding on the optical information recording media, irrespective of whether or not the optical information recording media has a hub, and irrespective of whether or not the media is housed in a cartridge.
B) Description of the Related Art
With the wide development of multimedia in recent years there has been an increasing need for effective application of optical information recording media which can store a large amount of information or data. Consequently, there has been a sharp increase in the development in recent years of a variety of optical information recording media. Specifically, various forms of disk-shaped optical information recording media have been developed.
Disk-shaped optical information recording media or optical disks can be classified as read-only, direct read after write and rewriteable types. Rewriteable types include magneto-optical types, phase-change (crystal-amorphous transformation) types, and organic pigment types. However, one of the more widely used types is the magneto-optical type disk which may be re-written over repeatedly.
Read-only types are widely used as video disks, compact disks (CD), CD-ROMs and the like. These are generally standardized, with a center hole bored at the center of a disk, and many of them are in use. Read-only types are configured to play back pre-recorded information using an optical head. Typically, such read-only disks are used by removing the read-only type disks from a protective storage case and placing them unhoused on the tray of a playback device. The tray retracts into a playback position, the disk is centered on a turntable, clamped in place and the information can be readily read by the optical head. Such read only-type disks are standardized having a diameter of 120 mm. The center hole formed in the disks is also a standard size.
The standard for direct read after write type and rewriteable type optical disks, was fixed in 1990 for the disks to have a diameter of 130 mm. Direct read after write type disks and rewriteable type disks are provided with a hub. The hub provides a means for centering the disk in a reading device and also provide a means for magnetic clamping within the reading device. The hubs typically include a thin magnetic metal plate disposed within a center hole bored in the disk. Such disks are also usually housed in a cartridge. The cartridge is inserted directly in a recording/playback device. Upon insertion, a shutter provided in the cartridge is opened by the device, the disk is centered on a turntable in the recording/playback device using the hub, the hub is magnetically affixed to a magnetic body which is provided on the turntable. It is then possible for the rewriteable type disk recording/playback device to record information on the rewriteable disk or read information from the rewriteable disk using an optical head and a recording magnetic head.
As described above, direct read after write type and rewriteable type disk recording/playback devices are uniform, having a standard centering method and clamping method. A plurality of like disks can be used in a single device. It is possible for the drive means, optical head and the like of a single recording/playback device to be standardized. However, read-only disks such as CDs and CD-ROMs use a different encoding method and the physical specifications of the read-only disks requires a different centering method and clamping method. Further, CDs and CD-ROMs may or may not be in a cartridge. Therefore the differing types of media, rewriteable and read-only disks are not interchangeable. For instance, it is not possible to use a direct read after write type and rewriteable type disks in a CD read-only type devices. Thus, playback devices for read-only disks, and recording/playback devices for direct read after write type and rewriteable type disks to date have been separately manufactured and sold.
The typical computer user therefore has been required to purchase multiple types of devices in order to use read-only type disks, direct read after write disks and the rewriteable type disks. The manufacture of playback devices for read-only optical disks, direct read after write disks and rewriteable optical disks requires the use of some similar components. For instance, all types of devices use similar drive means and similar expensive optical heads. Consequently, an end user must pay dearly for duplicative electronic components. Further, having separate disk devices requires the use of possibly valuable space in a computer chassis. If the computer user also needs to use other peripheral devices in the computer, such as floppy disks, and input/output machines such as image scanners, then it is even more desirable to use as little space as possible for optical based reading/writing devices.
Further, read-only optical information recording media such as CDs and CD-ROMs are removed from their protective case for use, and are inserted into the playback device. Hand dirt, fingerprints, dust and the like are liable to become adhered to the surface of the CD or CD-ROM during handling, and furthermore foreign bodies are liable to be transferred to the surface during playback of the CD or CD-ROM, thereby causing unsatisfactory playback of the information. In order to prevent this, it is preferable for arrangements to be made such that information can be played back while the CD or CD-ROM is still housed in a disk cartridge.